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Wed, 29 Apr 2015 09:40:42 +0200Wed, 29 Apr 2015 09:40:42 +0200Loss of lysosome-associated membrane protein 3 (LAMP3) enhances cellular vulnerability against proteasomal inhibitionhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/36629
The family of lysosome-associated membrane proteins (LAMP) includes the ubiquitously expressed LAMP1 and LAMP2, which account for half of the proteins in the lysosomal membrane. Another member of the LAMP family is LAMP3, which is expressed only in certain cell types and differentiation stages. LAMP3 expression is linked with poor prognosis of certain cancers, and the locus where it is encoded was identified as a risk factor for Parkinson's disease (PD). Here, we investigated the role of LAMP3 in the two main cellular degradation pathways, the proteasome and autophagy. LAMP3 mRNA was not detected in mouse models of PD or in the brain of human patients. However, it was strongly induced upon proteasomal inhibition in the neuroblastoma cell line SH-SY5Y. Induction of LAMP3 mRNA following proteasomal inhibition was dependent on UPR transcription factor ATF4 signaling and induced autophagic flux. Prevention of LAMP3 induction enhanced apoptotic cell death. In summary, these data demonstrate that LAMP3 regulation as part of the UPR contributes to protein degradation and cell survival during proteasomal dysfunction. This link between autophagy and the proteasome may be of special importance for the treatment of tumor cells with proteasomal inhibitors.Jorge Antolio Domínguez Bautista; Michael Klinkenberg; Nadine Brehm; Mahalakshmi Subramaniam; Beatrice Kern; Jochen Roeper; Georg Auburger; Marina Jendracharticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/36629Wed, 29 Apr 2015 09:40:42 +0200Both Ubiquitin Ligases FBXW8 and PARK2 Are Sequestrated into Insolubility by ATXN2 PolyQ Expansions, but Only FBXW8 Expression Is Dysregulatedhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/37167
The involvement of the ubiquitin-proteasome system (UPS) in the course of various age-associated neurodegenerative diseases is well established. The single RING finger type E3 ubiquitin-protein ligase PARK2 is mutated in a Parkinson’s disease (PD) variant and was found to interact with ATXN2, a protein where polyglutamine expansions cause Spinocerebellar ataxia type 2 (SCA2) or increase the risk for Levodopa-responsive PD and for the motor neuron disease Amyotrophic lateral sclerosis (ALS). We previously reported evidence for a transcriptional induction of the multi-subunit RING finger Skp1/Cul/F-box (SCF) type E3 ubiquitin-protein ligase complex component FBXW8 in global microarray profiling of ATXN2-expansion mouse cerebellum and demonstrated its role for ATXN2 degradation in vitro. Now, we documented co-localization in vitro and co-immunoprecipitations both in vitro and in vivo, which indicate associations of FBXW8 with ATXN2 and PARK2. Both FBXW8 and PARK2 proteins are driven into insolubility by expanded ATXN2. Whereas the FBXW8 transcript upregulation by ATXN2- expansion was confirmed also in qPCR of skin fibroblasts and blood samples of SCA2 patients, a FBXW8 expression dysregulation was not observed in ATXN2-deficient mice, nor was a PARK2 transcript dysregulation observed in any samples. Jointly, all available data suggest that the degradation of wildtype and mutant ATXN2 is dependent on FBXW8, and that ATXN2 accumulation selectively modulates FBXW8 levels, while PARK2 might act indirectly through FBXW8. The effects of ATXN2-expansions on FBXW8 expression in peripheral tissues like blood may become useful for clinical diagnosticsMelanie Vanessa Halbach; Tanja Stehning; Ewa Damrath; Marina Jendrach; Nesli Ece Şen; A. Nazlı Başak; Georg Auburgerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/37167Sun, 22 Mar 2015 19:32:28 +0100Loss of PINK1 impairs stress-induced autophagy and cell survivalhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33455
The mitochondrial kinase PINK1 and the ubiquitin ligase Parkin are participating in quality control after CCCP- or ROSinduced mitochondrial damage, and their dysfunction is associated with the development and progression of Parkinson’s disease. Furthermore, PINK1 expression is also induced by starvation indicating an additional role for PINK1 in stress response. Therefore, the effects of PINK1 deficiency on the autophago-lysosomal pathway during stress were investigated. Under trophic deprivation SH-SY5Y cells with stable PINK1 knockdown showed downregulation of key autophagic genes, including Beclin, LC3 and LAMP-2. In good agreement, protein levels of LC3-II and LAMP-2 but not of LAMP-1 were reduced in different cell model systems with PINK1 knockdown or knockout after addition of different stressors. This downregulation of autophagic factors caused increased apoptosis, which could be rescued by overexpression of LC3 or PINK1. Taken together, the PINK1-mediated reduction of autophagic key factors during stress resulted in increased cell death, thus defining an additional pathway that could contribute to the progression of Parkinson’s disease in patients with PINK1 mutations.Dajana Parganlija; Michael Klinkenberg; Jorge Domínguez-Bautista; Miriam Hetzel; Suzana Gispert; Marthe A. Chimi; Stefan Dröse; Sören Mai; Ulrich Brandt; Georg Auburger; Marina Jendracharticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33455Wed, 07 May 2014 11:11:52 +0200Alpha-synuclein deficiency leads to increased glyoxalase I expression and glycation stresshttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33421
The presynaptic protein alpha-synuclein has received much attention because its gain-of-function is associated with Parkinson’s disease. However, its physiological function is still poorly understood. We studied brain regions of knock-out mice at different ages with regard to consistent upregulations of the transcriptome and focused on glyoxalase I (GLO1). The microarray data were confirmed in qPCR, immunoblot, enzyme activity, and behavior analyses. GLO1 induction is a known protective cellular response to glucose stress, representing efforts to decrease toxic levels of methylglyoxal (MG), glyoxal and advanced glycation endproducts (AGEs). Mass spectrometry quantification demonstrated a ubiquitous increase in MG and fructosyl-lysine as consequences of glucose toxicity, and consistent enhancement of certain AGEs. Thus, GLO1 induction in KO brain seems insufficient to prevent AGE formation. In conclusion, the data demonstrate GLO1 expression and glycation damage to be induced by alpha-synuclein ablation. We propose that wild-type alpha-synuclein modulates brain glucose metabolism.Alexander Kurz; Naila Rabbani; Michael Walter; Michael Bonin; Paul Thornalley; Georg Auburger; Suzana Gispertperiodicalparthttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33421Mon, 07 Apr 2014 16:28:43 +0200The mitochondrial kinase PINK1, stress response and Parkinson’s diseasehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33420
Mitochondrial dysfunction is well documented in presymptomatic brain tissue with Parkinson's disease (PD). Identification of the autosomal recessive variant PARK6 caused by loss-of-function mutations in the mitochondrial kinase PINK1 provides an opportunity to dissect pathogenesis. Although PARK6 shows clinical differences to PD, the induction of alpha-synuclein "Lewy" pathology by PINK1-deficiency proves that mitochondrial pathomechanisms are relevant for old-age PD. Mitochondrial dysfunction is induced by PINK1 deficiency even in peripheral tissues unaffected by disease, consistent with the ubiquitous expression of PINK1. It remains unclear whether this dysfunction is due to PINK1-mediated phosphorylation of proteins inside or outside mitochondria. Although PINK1 deficiency affects the mitochondrial fission/fusion balance, cell stress is required in mammals to alter mitochondrial dynamics and provoke apoptosis. Clearance of damaged mitochondria depends on pathways including PINK1 and Parkin and is critical for postmitotic neurons with high energy demand and cumulative stress, providing a mechanistic concept for the tissue specificity of disease.Marina Jendrach; Suzana Gispert; Filomena Ricciardi; Michael Klinkenberg; Rudolf Schemm; Georg Auburgerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33420Mon, 07 Apr 2014 13:30:22 +0200Dysregulated expression of lipid storage and membrane dynamics factors in Tia1 knockout mouse nervous tissuehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33422
During cell stress, the transcription and translation of immediate early genes are prioritized, while most other messenger RNAs (mRNAs) are stored away in stress granules or degraded in processing bodies (P-bodies). TIA-1 is an mRNA-binding protein that needs to translocate from the nucleus to seed the formation of stress granules in the cytoplasm. Because other stress granule components such as TDP-43, FUS, ATXN2, SMN, MAPT, HNRNPA2B1, and HNRNPA1 are crucial for the motor neuron diseases amyotrophic lateral sclerosis (ALS)/spinal muscular atrophy (SMA) and for the frontotemporal dementia (FTD), here we studied mouse nervous tissue to identify mRNAs with selective dependence on Tia1 deletion. Transcriptome profiling with oligonucleotide microarrays in comparison of spinal cord and cerebellum, together with independent validation in quantitative reverse transcriptase PCR and immunoblots demonstrated several strong and consistent dysregulations. In agreement with previously reported TIA1 knock down effects, cell cycle and apoptosis regulators were affected markedly with expression changes up to +2-fold, exhibiting increased levels for Cdkn1a, Ccnf, and Tprkb vs. decreased levels for Bid and Inca1 transcripts. Novel and surprisingly strong expression alterations were detected for fat storage and membrane trafficking factors, with prominent +3-fold upregulations of Plin4, Wdfy1, Tbc1d24, and Pnpla2 vs. a −2.4-fold downregulation of Cntn4 transcript, encoding an axonal membrane adhesion factor with established haploinsufficiency. In comparison, subtle effects on the RNA processing machinery included up to 1.2-fold upregulations of Dcp1b and Tial1. The effect on lipid dynamics factors is noteworthy, since also the gene deletion of Tardbp (encoding TDP-43) and Atxn2 led to fat metabolism phenotypes in mouse. In conclusion, genetic ablation of the stress granule nucleator TIA-1 has a novel major effect on mRNAs encoding lipid homeostasis factors in the brain, similar to the fasting effect.Melanie Vanessa Heck; Mekhman Azizov; Tanja Stehning; Michael Walter; Nancy Kedersha; Georg Auburgerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33422Fri, 04 Apr 2014 09:20:10 +0200Ataxin-2 Modulates the Levels of Grb2 and Src but Not Ras Signalinghttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33351
Ataxin-2 (ATXN2) is implicated mainly in mRNA processing. Some ATXN2 associates with receptor tyrosine kinases (RTK), inhibiting their endocytic internalization through interaction of proline-rich domains (PRD) in ATXN2 with SH3 motifs in Src. Gain of function of ATXN2 leads to neuronal atrophy in the diseases spinocerebellar ataxia type 2 (SCA2) and amyotrophic lateral sclerosis (ALS). Conversely, ATXN2 knockout (KO) mice show hypertrophy and insulin resistance. To elucidate the influence of ATXN2 on trophic regulation, we surveyed interactions of ATXN2 with SH3 motifs from numerous proteins and observed a novel interaction with Grb2. Direct binding in glutathione S-transferase (GST) pull-down assays and coimmunoprecipitation of the endogenous proteins indicated a physiologically relevant association. In SCA2 patient fibroblasts, Grb2 more than Src protein levels were diminished, with an upregulation of both transcripts suggesting enhanced protein turnover. In KO mouse embryonal fibroblasts (MEF), the protein levels of Grb2 and Src were decreased. ATXN2 absence by itself was insufficient to significantly change Grb2-dependent signaling for endogenous Ras levels, Ras-GTP levels, and kinetics as well as MEK1 phosphorylation, suggesting that other factors compensate for proliferation control. In KO tissue with postmitotic neurons, a significant decrease of Src protein levels is prominent rather than Grb2. ATXN2 mutations modulate the levels of several components of the RTK endocytosis complex and may thus contribute to alter cell proliferation as well as translation and growth.Jessica Drost; David Nonis; Florian Eich; Oliver Leske; Ewa Damrath; Ewout R. Brunt; Isabel Lastres-Becker; Rolf Heumann; Joachim Nowock; Georg Auburgerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/33351Thu, 03 Apr 2014 17:40:07 +0200Spinocerebellar Ataxia Type 2http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/31709
1. Introduction: The autosomal dominant cerebellar ataxias (ADCA) are a clinically, pathologically and genetically heterogeneous group of neurodegenerative disorders caused by degeneration of cerebellum and its afferent and efferent connections. The degenerative process may additionally involves the ponto- medullar systems, pyramidal tracts, basal ganglia, cerebral cortex, peripheral nerves (ADCA I) and the retina (ADCA II), or can be limited to the cerebellum (ADCA III) (Harding et al., 1993). The most common of these dominantly inherited autosomal ataxias, ADCA I, includes many Spinocerebellar Ataxias (SCA) subtypes, some of which are caused by pathological CAG trinucleotide repeat expansion in the coding region on the mutated gene. Such is the case for SCA1, SCA2, SCA3/MJD, SCA6, SCA7, SCA17 and Dentatorubral-pallidoluysian atrophy (DRPLA) (Matilla et al., 2006). Among the almost 30 SCAs, the variant SCA2 is the second most prevalent subtype worldwide, only surpassed by SCA3 (Schöls et al., 2004; Matilla et al., 2006; Auburger, 2011)...Luis Velázquez-Pérez; Roberto Rodríguez-Labrada; Hans-Joachim Freund; Georg Auburgerbookparthttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/31709Fri, 04 Oct 2013 11:23:14 +0200A53T-alpha-synuclein-overexpression in the mouse nigrostriatal pathway leads to early increase of 14-3-3 epsilon and late increase of GFAPhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/28308
Parkinson’s disease (PD) is a neurodegenerative disorder frequent at old age characterized by atrophy of the nigrostriatal projection. Overexpression and A53T-mutation of the presynaptic, vesicle-associated chaperone alpha-synuclein are known to cause early-onset autosomal dominant PD. We previously generated mice with transgenic overexpression of human A53T-alpha-synuclein (A53T-SNCA) in dopaminergic substantia nigra neurons as a model of early PD. To elucidate the early and late effects of A53T-alpha-synuclein on the proteome of dopaminergic nerve terminals in the striatum, we now investigated expression profiles of young and old mice using two-dimensional fluorescence difference in gel electrophoresis (2D-DIGE) and mass spectrometry. In total, 15 proteins were upregulated and 2 downregulated. Mice before the onset of motor anomalies showed an upregulation of the spot containing 14-3-3 proteins, in particular the epsilon isoform, as well as altered levels of chaperones, vesicle trafficking and bioenergetics proteins. In old mice, the persistent upregulation of 14-3-3 proteins was aggravated by an increase of glial fibrillary acidic protein (GFAP) suggesting astrogliosis due to initial neurodegeneration. Independent immunoblots corroborated GFAP upregulation and 14-3-3 upregulation for the epsilon isoform, and also detected significant eta and gamma changes. Only for 14-3-3 epsilon a corresponding mRNA increase was observed in midbrain, suggesting it is transcribed in dopaminergic perikarya and accumulates as protein in presynapses, together with A53T-SNCA. 14-3-3 proteins associate with alpha-synuclein in vitro and in pathognomonic Lewy bodies of PD brains. They act as chaperones in signaling, dopamine synthesis and stress response. Thus, their early dysregulation probably reflects a response to alpha-synuclein toxicity.
Electronic supplementary material: The online version of this article (doi:10.1007/s00702-011-0717-3) contains supplementary material, which is available to authorized users.Alexander Kurz; Caroline May; Oliver Schmidt; Thorsten Müller; Christian Stephan; Helmut E. Meyer; Suzana Gispert; Georg Auburger; Katrin Marcusarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/28308Thu, 19 Sep 2013 15:43:21 +0200Restriction of trophic factors and nutrients induces PARKIN expressionhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/29905
Parkinson's disease (PD) is the most frequent neurodegenerative movement disorder and manifests at old age. While many details of its pathogenesis remain to be elucidated, in particular the protein and mitochondrial quality control during stress responses have been implicated in monogenic PD variants. Especially the mitochondrial kinase PINK1 and the ubiquitin ligase PARKIN are known to cooperate in autophagy after mitochondrial damage. As autophagy is also induced by loss of trophic signaling and PINK1 gene expression is modulated after deprivation of cytokines, we analyzed to what extent trophic signals and starvation stress regulate PINK1 and PARKIN expression. Time course experiments with serum deprivation and nutrient starvation of human SH-SY5Y neuroblastoma cells and primary mouse neurons demonstrated phasic induction of PINK1 transcript up to twofold and PARKIN transcript levels up to sixfold. The corresponding threefold starvation induction of PARKIN protein was limited by its translocation to lysosomes. Analysis of primary mouse cells from PINK1-knockout mice indicated that PARKIN induction and lysosomal translocation occurred independent of PINK1. Suppression of the PI3K-Akt-mTOR signaling by pharmacological agents modulated PARKIN expression accordingly. In conclusion, this expression survey demonstrates that PARKIN and PINK1 are coregulated during starvation and suggest a role of both PD genes in response to trophic signals and starvation stress.Michael Klinkenberg; Suzana Gispert; Jorge Antolio Dominguez Bautista; Isabelle Braun; Georg Auburger; Marina Jendracharticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/29905Mon, 13 May 2013 16:23:10 +0200Primary skin fibroblasts as a model of Parkinson's diseasehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/27964
Parkinson's disease is the second most frequent neurodegenerative disorder. While most cases occur sporadic mutations in a growing number of genes including Parkin (PARK2) and PINK1 (PARK6) have been associated with the disease. Different animal models and cell models like patient skin fibroblasts and recombinant cell lines can be used as model systems for Parkinson's disease. Skin fibroblasts present a system with defined mutations and the cumulative cellular damage of the patients. PINK1 and Parkin genes show relevant expression levels in human fibroblasts and since both genes participate in stress response pathways, we believe fibroblasts advantageous in order to assess, e.g. the effect of stressors. Furthermore, since a bioenergetic deficit underlies early stage Parkinson's disease, while atrophy underlies later stages, the use of primary cells seems preferable over the use of tumor cell lines. The new option to use fibroblast-derived induced pluripotent stem cells redifferentiated into dopaminergic neurons is an additional benefit. However, the use of fibroblast has also some drawbacks. We have investigated PARK6 fibroblasts and they mirror closely the respiratory alterations, the expression profiles, the mitochondrial dynamics pathology and the vulnerability to proteasomal stress that has been documented in other model systems. Fibroblasts from patients with PARK2, PARK6, idiopathic Parkinson's disease, Alzheimer's disease, and spinocerebellar ataxia type 2 demonstrated a distinct and unique mRNA expression pattern of key genes in neurodegeneration. Thus, primary skin fibroblasts are a useful Parkinson's disease model, able to serve as a complement to animal mutants, transformed cell lines and patient tissues.Georg Auburger; Michael Klinkenberg; Jessica Drost; Katrin Marcus; Blas Morales-Gordo; Wolfram S. Kunz; Ulrich Brandt; Vania Broccoli; Heinz Reichmann; Suzana Gispert; Marina Jendracharticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/27964Fri, 01 Feb 2013 14:52:10 +0100ATXN2-CAG42 sequesters PABPC1 into insolubility and induces FBXW8 in cerebellum of old ataxic knock-in micehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25925
Spinocerebellar Ataxia Type 2 (SCA2) is caused by expansion of a polyglutamine encoding triplet repeat in the human ATXN2 gene beyond (CAG)31. This is thought to mediate toxic gain-of-function by protein aggregation and to affect RNA processing, resulting in degenerative processes affecting preferentially cerebellar neurons. As a faithful animal model, we generated a knock-in mouse replacing the single CAG of murine Atxn2 with CAG42, a frequent patient genotype. This expansion size was inherited stably. The mice showed phenotypes with reduced weight and later motor incoordination. Although brain Atxn2 mRNA became elevated, soluble ATXN2 protein levels diminished over time, which might explain partial loss-of-function effects. Deficits in soluble ATXN2 protein correlated with the appearance of insoluble ATXN2, a progressive feature in cerebellum possibly reflecting toxic gains-of-function. Since in vitro ATXN2 overexpression was known to reduce levels of its protein interactor PABPC1, we studied expansion effects on PABPC1. In cortex, PABPC1 transcript and soluble and insoluble protein levels were increased. In the more vulnerable cerebellum, the progressive insolubility of PABPC1 was accompanied by decreased soluble protein levels, with PABPC1 mRNA showing no compensatory increase. The sequestration of PABPC1 into insolubility by ATXN2 function gains was validated in human cell culture. To understand consequences on mRNA processing, transcriptome profiles at medium and old age in three different tissues were studied and demonstrated a selective induction of Fbxw8 in the old cerebellum. Fbxw8 is encoded next to the Atxn2 locus and was shown in vitro to decrease the level of expanded insoluble ATXN2 protein. In conclusion, our data support the concept that expanded ATXN2 undergoes progressive insolubility and affects PABPC1 by a toxic gain-of-function mechanism with tissuespecific effects, which may be partially alleviated by the induction of FBXW8.Ewa Damrath; Melanie V. Heck; Suzana Gispert; Mekhman Azizov; Joachim Nowock; Carola Seifried; Udo Rüb; Michael Walter; Georg Auburgerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25925Sun, 02 Sep 2012 15:35:04 +0200ATXN2 and its neighbouring gene SH2B3 are associated with increased ALS risk in the Turkish populationhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25857
Expansions of the polyglutamine (polyQ) domain (≥34) in Ataxin-2 (ATXN2) are the primary cause of spinocerebellar ataxia type 2 (SCA2). Recent studies reported that intermediate-length (27–33) expansions increase the risk of Amyotrophic Lateral Sclerosis (ALS) in 1–4% of cases in diverse populations. This study investigates the Turkish population with respect to ALS risk, genotyping 158 sporadic, 78 familial patients and 420 neurologically healthy controls. We re-assessed the effect of ATXN2 expansions and extended the analysis for the first time to cover the ATXN2 locus with 18 Single Nucleotide Polymorphisms (SNPs) and their haplotypes. In accordance with other studies, our results confirmed that 31–32 polyQ repeats in the ATXN2 gene are associated with risk of developing ALS in 1.7% of the Turkish ALS cohort (p = 0.0172). Additionally, a significant association of a 136 kb haplotype block across the ATXN2 and SH2B3 genes was found in 19.4% of a subset of our ALS cohort and in 10.1% of the controls (p = 0.0057, OR: 2.23). ATXN2 and SH2B3 encode proteins that both interact with growth receptor tyrosine kinases. Our novel observations suggest that genotyping of SNPs at this locus may be useful for the study of ALS risk in a high percentage of individuals and that ATXN2 and SH2B3 variants may interact in modulating the disease pathway.Suna Lahut; Özgür Ömür; Özgün Uyan; Zeynep Sena Ağım; Aslihan Özoğuz; Yeşim Parman; Feza Deymeer; Piraye Oflazer; Filiz Koç; Hilmi Özçelik; Georg Auburger; A. Nazlı Başakarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25857Fri, 24 Aug 2012 13:16:12 +0200Striatal dopamine transmission is subtly modified in human A53Tα-synuclein overexpressing micehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/24337
Mutations in, or elevated dosage of, SNCA, the gene for α-synuclein (α-syn), cause familial Parkinson's disease (PD). Mouse lines overexpressing the mutant human A53Tα-syn may represent a model of early PD. They display progressive motor deficits, abnormal cellular accumulation of α-syn, and deficits in dopamine-dependent corticostriatal plasticity, which, in the absence of overt nigrostriatal degeneration, suggest there are age-related deficits in striatal dopamine (DA) signalling. In addition A53Tα-syn overexpression in cultured rodent neurons has been reported to inhibit transmitter release. Therefore here we have characterized for the first time DA release in the striatum of mice overexpressing human A53Tα-syn, and explored whether A53Tα-syn overexpression causes deficits in the release of DA. We used fast-scan cyclic voltammetry to detect DA release at carbon-fibre microelectrodes in acute striatal slices from two different lines of A53Tα-syn-overexpressing mice, at up to 24 months. In A53Tα-syn overexpressors, mean DA release evoked by a single stimulus pulse was not different from wild-types, in either dorsal striatum or nucleus accumbens. However the frequency responsiveness of DA release was slightly modified in A53Tα-syn overexpressors, and in particular showed slight deficiency when the confounding effects of striatal ACh acting at presynaptic nicotinic receptors (nAChRs) were antagonized. The re-release of DA was unmodified after single-pulse stimuli, but after prolonged stimulation trains, A53Tα-syn overexpressors showed enhanced recovery of DA release at old age, in keeping with elevated striatal DA content. In summary, A53Tα-syn overexpression in mice causes subtle changes in the regulation of DA release in the striatum. While modest, these modifications may indicate or contribute to striatal dysfunction.Nicola J. Platt; Suzana Gispert; Georg Auburger; Stephanie J. Craggarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/24337Wed, 23 May 2012 17:03:38 +0200The role of glyoxalases for sugar stress and aging, with relevance for dyskinesia, anxiety, dementia and Parkinson's diseasehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/16682
Commentary on: Scheckhuber CQ et al. Modulation of the glyoxalase system in the aging model Podospora anserina: effects on growth and lifespan. Aging. 2010; 2: 969-980.Georg Auburger; Alexander Kurzarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/16682Thu, 14 Apr 2011 16:22:14 +0200A53T-alpha-synuclein overexpression impairs dopamine signaling and striatal synaptic plasticity in old micehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/20232
BACKGROUND: Parkinson's disease (PD), the second most frequent neurodegenerative disorder at old age, can be caused by elevated expression or the A53T missense mutation of the presynaptic protein alpha-synuclein (SNCA). PD is characterized pathologically by the preferential vulnerability of the dopaminergic nigrostriatal projection neurons. METHODOLOGY/PRINCIPAL FINDINGS: Here, we used two mouse lines overexpressing human A53T-SNCA and studied striatal dysfunction in the absence of neurodegeneration to understand early disease mechanisms. To characterize the progression, we employed young adult as well as old mice. Analysis of striatal neurotransmitter content demonstrated that dopamine (DA) levels correlated directly with the level of expression of SNCA, an observation also made in SNCA-deficient (knockout, KO) mice. However, the elevated DA levels in the striatum of old A53T-SNCA overexpressing mice may not be transmitted appropriately, in view of three observations. First, a transcriptional downregulation of the extraneural DA degradation enzyme catechol-ortho-methytransferase (COMT) was found. Second, an upregulation of DA receptors was detected by immunoblots and autoradiography. Third, extensive transcriptome studies via microarrays and quantitative real-time RT-PCR (qPCR) of altered transcript levels of the DA-inducible genes Atf2, Cb1, Freq, Homer1 and Pde7b indicated a progressive and genotype-dependent reduction in the postsynaptic DA response. As a functional consequence, long term depression (LTD) was absent in corticostriatal slices from old transgenic mice. CONCLUSIONS/SIGNIFICANCE: Taken together, the dysfunctional neurotransmission and impaired synaptic plasticity seen in the A53T-SNCA overexpressing mice reflect early changes within the basal ganglia prior to frank neurodegeneration. As a model of preclinical stages of PD, such insights may help to develop neuroprotective therapeutic approaches.Alexander Kurz; Kay L. Double; Isabel Lastres-Becker; Alessandro Tozzi; Michela Tantucci; Vanessa Bockhart; Michael Bonin; Moisés García-Arencibia; Silke Nuber; Falk Schlaudraff; Birgit Liss; Javier Fernández-Ruiz; Manfred Gerlach; Ullrich Wüllner; Hartmut Lüddens; Paolo Calabresi; Georg Auburger; Suzana Gispertarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/20232Thu, 11 Nov 2010 15:35:36 +0100Solving a 50 year mystery of a missing OPA1 mutation: more insights from the first family diagnosed with autosomal dominant optic atrophyhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/7862
Background: Up to the 1950s, there was an ongoing debate about the diversity of hereditary optic neuropathies, in particular as to whether all inherited optic atrophies can be ascribed to Leber's hereditary optic neuropathy (LHON) or represent different disease entities. In 1954 W. Jaeger published a detailed clinical and genealogical investigation of a large family with explicit autosomal dominant segregation of optic atrophy thus proving the existence of a discrete disease different from LHON, which is nowadays known as autosomal dominant optic atrophy (ADOA). Since the year 2000 ADOA is associated with genomic mutations in the OPA1 gene, which codes for a protein that is imported into mitochondria where it is required for mitochondrial fusion. Interestingly enough, the underlying mutation in this family has not been identified since then. Results: We have reinvestigated this family with the aim to identify the mutation and to further clarify the underlying pathomechanism. Patients showed a classical non-syndromic ADOA. The long term deterioration in vision in the two teenagers examined 50 years later is of particular note 5/20 to 6/120. Multiplex ligation probe amplification revealed a duplication of the OPA1 exons 7-9 which was confirmed by long distance PCR and cDNA analysis, resulting in an in-frame duplication of 102 amino acids. Segregation was verified in 53 available members of the updated pedigree and a penetrance of 88% was calculated. Fibroblast cultures from skin biopsies were established to assess the mitochondrial network integrity and to qualitatively and quantitatively study the consequences of the mutation on transcript and protein level. Fibroblast cultures demonstrated a fragmented mitochondrial network. Processing of the OPA1 protein was altered. There was no correlation of the OPA1 transcript levels and the OPA1 protein levels in the fibroblasts. Intriguingly an overall decrease of mitochondrial proteins was observed in patients' fibroblasts, while the OPA1 transcript levels were elevated. Conclusions: The thorough study of this family provides a detailed clinical picture accompanied by a molecular investigation of patients' fibroblasts. Our data show a classic OPA1-associated non-syndromic ADOA segregating in this family. Cell biological findings suggest that OPA1 is regulated by post-translational mechanisms and we would like to hypothesize that loss of OPA1 function might lead to impaired mitochondrial quality control. With the clinical, genetic and cell biological characterisation of a family described already more than 50 years ago, we span more than half a century of research in optic neuropathies.Nico Fuhrmann; Simone Schimpf; York Kamenisch; Beate Leo-Kottler; Christiane Alexander; Georg Auburger; Eberhart Zrenner; Bernd Wissinger; Marcel Victor Alavi-Khorassani Moghadamarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/7862Tue, 10 Aug 2010 12:09:58 +0200Parkinson phenotype in aged PINK1-deficient mice is accompanied by progressive mitochondrial dysfunction in absence of neurodegenerationhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6722
Background Parkinson's disease (PD) is an adult-onset movement disorder of largely unknown etiology. We have previously shown that loss-of-function mutations of the mitochondrial protein kinase PINK1 (PTEN induced putative kinase 1) cause the recessive PARK6 variant of PD. Methodology/Principal Findings Now we generated a PINK1 deficient mouse and observed several novel phenotypes: A progressive reduction of weight and of locomotor activity selectively for spontaneous movements occurred at old age. As in PD, abnormal dopamine levels in the aged nigrostriatal projection accompanied the reduced movements. Possibly in line with the PARK6 syndrome but in contrast to sporadic PD, a reduced lifespan, dysfunction of brainstem and sympathetic nerves, visible aggregates of alpha-synuclein within Lewy bodies or nigrostriatal neurodegeneration were not present in aged PINK1-deficient mice. However, we demonstrate PINK1 mutant mice to exhibit a progressive reduction in mitochondrial preprotein import correlating with defects of core mitochondrial functions like ATP-generation and respiration. In contrast to the strong effect of PINK1 on mitochondrial dynamics in Drosophila melanogaster and in spite of reduced expression of fission factor Mtp18, we show reduced fission and increased aggregation of mitochondria only under stress in PINK1-deficient mouse neurons. Conclusion Thus, aging Pink1 -/- mice show increasing mitochondrial dysfunction resulting in impaired neural activity similar to PD, in absence of overt neuronal death.Suzana Gispert; Filomena Ricciardi; Alexander Kurz; Mekhman Azizov; Hans-Hermann Hoepken; Dorothea Becker; Wolfgang Voos; Kristina Leuner; Walter E. Müller; Alexei P. Kudin; Wolfram S. Kunz; Annabelle Zimmermann; Jochen Roeper; Dirk Wenzel; Marina Jendrach; Moisés García-Arencíbia; Javier Fernández-Ruiz; Leslie Huber; Hermann Rohrer; Miguel Barrera; Andreas S. Reichert; Udo Rüb; Amy Chen; Robert L. Nussbaum; Georg Auburgerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6722Tue, 11 Aug 2009 16:21:20 +0200Rost, Müll oder Staus? : Parkinson aus der Sicht der molekularen Neurogenetikhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3511
Blutproben und Gewebe von Familien mit erblich bedingten degenerativen Erkrankungen wie Parkinson sind ein zentrales Forschungsobjekt der neu eingerichteten Forschungsprofessur »Molekulare Neurogenetik« innerhalb der Neurologischen Klinik der Universität Frankfurt. Sind die verantwortlichen Mutationen identifiziert, werden sie im Hirngewebe von Mäusen künstlich erzeugt. Aus der Untersuchung der krankhaften Veränderungen lassen sich Diagnostik und Therapie weiter entwickeln. Als bisherigen Höhepunkt unserer Forschungstätigkeit haben wir in einigen Parkinson- Familien als Krankheitsursache den Funktionsverlust eines Eiweißes namens PINK1 in den Mitochondrien nachgewiesen. Aufgrund dieser Beobachtung lässt sich oxidativer Stress als auslösender Schritt im Krankheitsgeschehen interpretieren. Experimentelle Therapien mit anti-oxidativen Medikamenten sind in Zellkultur getestet worden und sollen künftig auch im Mausmodell zum Einsatz kommen.Georg Auburgerarticlehttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3511Mon, 29 Oct 2007 09:13:02 +0100